WO2019069938A1 - ホットスタンプ成形品およびホットスタンプ用鋼板ならびにそれらの製造方法 - Google Patents
ホットスタンプ成形品およびホットスタンプ用鋼板ならびにそれらの製造方法 Download PDFInfo
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- WO2019069938A1 WO2019069938A1 PCT/JP2018/036913 JP2018036913W WO2019069938A1 WO 2019069938 A1 WO2019069938 A1 WO 2019069938A1 JP 2018036913 W JP2018036913 W JP 2018036913W WO 2019069938 A1 WO2019069938 A1 WO 2019069938A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/02—Stamping using rigid devices or tools
- B21D22/022—Stamping using rigid devices or tools by heating the blank or stamping associated with heat treatment
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
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- C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
- C23C2/0224—Two or more thermal pretreatments
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
- C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
- C23C2/40—Plates; Strips
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
Definitions
- the present invention relates to a hot stamped molded article, a steel plate for hot stamping, and a method of manufacturing the same.
- Priority is claimed on Japanese Patent Application No. 2017-193095, filed Oct. 02, 2017, the content of which is incorporated herein by reference.
- the materials used in each technical field are required to have special and high performance.
- high strength is required in order to improve fuel efficiency by reducing the weight of the vehicle body from the consideration to the global environment.
- desired strength can be imparted to the car body while reducing the thickness of the steel plate to reduce the weight of the car body.
- press forming which is a process of forming a vehicle body member of an automobile
- the thickness of a steel plate used is thinner, cracks and wrinkles are more likely to occur. Therefore, steel sheets for automobiles are also required to have excellent press formability.
- Patent Document 1 a technique of press-forming a heated steel plate using a low-temperature press die has been proposed.
- This technique is called hot stamping or hot pressing and the like, and since a steel plate heated to a high temperature and in a soft state is press-formed, it is possible to manufacture a member having a complicated shape with high dimensional accuracy. Further, since the steel sheet is rapidly cooled by the contact with the mold, it is possible to significantly increase the strength simultaneously with press forming by quenching.
- Patent Document 1 describes that a member having a tensile strength of 1400 MPa or more can be obtained by hot stamping a steel plate having a tensile strength of 500 to 600 MPa.
- Patent Document 2 discloses a method of partially changing the heating temperature of a steel plate by induction heating or infrared heating to soften a portion heated to a low temperature ing.
- Patent Document 3 discloses a method of attaching a heat insulating material to a part of a steel plate at the time of furnace heating the steel plate and partially lowering the heating temperature to soften the steel plate.
- Patent Document 4 and Patent Document 5 disclose a method of partially changing the cooling rate of a steel plate by changing the contact area between the steel plate and the mold at the time of molding, thereby softening a portion with a low cooling rate.
- Patent Document 6 discloses a technique of hot stamping using a so-called tailored blank material in which two base plates are welded and connected.
- Patent Documents 2 to 5 In hot stamping, usually, a steel sheet is heated to an austenite region and then cooled at a cooling rate higher than a critical cold rate to form a single structure of martensite and to strengthen the steel.
- the heating temperature or the cooling rate of the steel plate is partially lowered to generate a structure other than martensite to achieve softening.
- the fraction of the structure other than martensite is sensitively changed in response to the heating temperature and the cooling rate, the methods of Patent Documents 2 to 5 have a problem that the strength of the soft part is not stable.
- a soft part can be formed under a fixed heating-cooling condition by using a steel plate with low hardenability for one base plate.
- Patent Document 6 does not give any consideration to the component composition of the steel sheet having low hardenability.
- Patent Documents 7 and 8 disclose methods for stabilizing the strength of the soft portion in a hot stamp member consisting of a hard portion and a soft portion, or a hot stamp member that is entirely soft. It is done. Specifically, Patent Document 7 has a low C content and contains a certain amount or more of a hardening element, and suppresses formation of ferrite, pearlite and martensite during cooling, and thus, high strength for automobiles of 600 to 1200 MPa class. A component and a method of manufacturing the same are disclosed. Further, Patent Document 8 discloses a hot stamp member having a tensile strength of 500 MPa or more and a method of manufacturing the same, in which the C content is limited to a lower value and Ti is contained to control the formation amount of martensite. .
- Patent Documents 7 and 8 it is possible to improve the uniformity of strength and elongation in the member.
- the metal structure contains a hard structure such as bainite or martensite, the thermal stability is low, and the strength may decrease when the member is subjected to a paint baking treatment. It turned out that there is. In the case of automobile members, paint baking is often performed, so there is room for improvement in the techniques described in Patent Documents 7 and 8.
- Japanese Patent Application Laid-Open No. 2002-102980 Japanese Patent Application Laid-Open No. 2005-193287 Japan JP 2009-61473 Japanese Patent Application Laid-Open No. 2003-328031 WO 2006/38868 pamphlet Japanese Patent Application Laid-Open No. 2004-58082 Japanese Patent Application Laid-Open No. 2005-248320 WO 2008/132303 pamphlet
- the present invention solves the above-mentioned problems, and is excellent in thermal stability, more specifically, the variation of the strength (tensile strength) before and after the paint baking treatment accompanying the paint baking treatment is small, the tensile strength is 700 MPa It is an object of the present invention to provide a hot stamped molded article having a portion that is less than 100%, a hot stamping steel plate suitable as the material thereof, and a method of manufacturing them.
- the present invention has been made to solve the above-mentioned problems, and the gist of the following hot stamped molded article, steel plate for hot stamping and a method of manufacturing them.
- the hot stamped molded article according to an aspect of the present invention is a hot stamped molded article, and all or a part of the hot stamped molded article is, by mass%, C: 0.001% or more, 0.080 %, Si: 2.50% or less, Mn: 0.01% to 0.50%, P: 0.200% or less, S: 0.0200% or less, sol.
- the metallographic structure includes, by volume, ferrite: more than 60.0%, martensite: 0% or more and less than 10.0%, bainite: 0% or more and less than 20.0%, and tensile strength is The amount of decrease in tensile strength, ⁇ TS, which is less than 700 MPa and subjected to heat treatment at 170 ° C.
- the chemical composition is, by mass%, Ti: 0.001 to 0.300%, Nb: 0.001 to 0.300%, V: 0 It may contain one or more selected from .001 to 0.300%, and Zr: 0.001 to 0.300%.
- the chemical composition is, by mass%, Mo: 0.001 to 2.00%, Cu: 0.001 to 2.00% And Ni: one or more selected from 0.001 to 2.00%.
- the chemical composition may contain B: 0.0001 to 0.0200% by mass.
- the chemical composition is, by mass%, Ca: 0.0001 to 0.0100%, Mg: 0.0001 to 0 One or more selected from 0100% and REM: 0.0001 to 0.1000% may be contained.
- the chemical composition may contain Bi: 0.0001 to 0.0500% by mass.
- the hot stamped molded article according to any one of the above (1) to (6) may have a plating layer on the surface.
- the steel sheet for hot stamping according to another aspect of the present invention has a chemical composition of, in mass%, C: 0.001% or more and less than 0.080%, Si: 2.50% or less, Mn: 0. 01% or more and less than 0.50%, P: 0.200% or less, S: 0.0200% or less, sol.
- the steel sheet for hot stamping as described in (8) or (9) above has the chemical composition represented by mass%, Mo: 0.001 to 2.00%, Cu: 0.001 to 2.00% And Ni: one or more selected from 0.001 to 2.00%.
- the steel plate for hot stamping according to any one of the above (8) to (10) may contain B: 0.0001 to 0.0200% by mass as the chemical composition.
- One or more selected from 0100% and REM: 0.0001 to 0.1000% may be contained.
- the steel sheet for hot stamping according to any one of the above (8) to (12) may contain Bi: 0.0001 to 0.0500% by mass as the chemical composition.
- the steel plate for hot stamping according to any one of the above (8) to (13) may have a plating layer on the surface.
- a method for producing a hot stamped article according to another aspect of the present invention is a method for producing a hot stamped article according to any one of (1) to (6) above, A heating step of heating the steel plate for hot stamping according to any one of (13) to a heating temperature T ° C., and a hot stamping step of hot stamping the steel plate for hot stamping after the heating step.
- a method for producing a hot stamped article according to another aspect of the present invention is a method for producing a hot stamped article according to any one of the above (1) to (6), which comprises A joining step of joining the steel plate for hot stamping according to any one of (13) with a joining steel plate to form a joining steel plate, a heating step of heating the joining steel plate after the joining step to a heating temperature T ° C., And a hot stamping step of hot stamping the bonded steel sheet after the heating step.
- a method for producing a hot stamped article according to another aspect of the present invention is a method for producing a hot stamped article according to (7) above, which comprises the steel sheet for hot stamping according to (14) And a hot stamping process for hot stamping the steel plate for hot stamping after the heating process.
- a method for producing a hot stamped article according to another aspect of the present invention is a method for producing a hot stamped article according to (7) above, which comprises the steel sheet for hot stamping according to (14) Performing a hot stamping on the bonding steel plate after the bonding step, a bonding step of bonding with the bonding steel plate to form a bonding steel plate, a heating step of heating the bonding steel plate after the bonding step to a heating temperature T ° C.
- the heating temperature T ° C is a temperature exceeding Ac 1 point of the steel plate for hot stamping
- the hot stamping start temperature may be (T-300) ° C. or higher.
- the method for producing a hot stamping steel plate according to another aspect of the present invention is a method for producing a hot stamping steel plate according to any one of (8) to (14), wherein the chemical composition is mass %, C: 0.001% or more and less than 0.080%, Si: 2.50% or less, Mn: 0.01% or more and less than 0.50%, P: 0.200% or less, S: 0.0200 % Or less, sol.
- the method for producing a steel plate for hot stamping according to the above (20) further comprises optionally performing either or both of cold rolling and annealing on the hot-rolled annealed steel plate after the hot-rolled sheet annealing step
- the plating process may be performed after plating.
- FIG. 2 is a schematic view showing the shape of the hot stamped molded product manufactured in Example 1
- FIG. 6 is a schematic view showing the shape of the hot stamped molded product produced in Example 2.
- the inventors of the present invention have keenly studied a method for suppressing a reduction in strength at the baking process of a hot stamped product having a tensile strength of less than 700 MPa. As a result, the following findings were obtained.
- C 0.001% or more and less than 0.080% C is an element having an effect of increasing the tensile strength of the steel plate after hot stamping (the steel plate provided in the hot stamped molded product). If the C content is less than 0.001%, the increase in tensile strength due to hot stamping can not be expected.
- the preferred C content is 0.010% or more, 0.020% or more, or 0.030% or more.
- the C content is 0.080% or more, the volume fraction of martensite and / or bainite increases in the metal structure after hot stamping, and the tensile strength of the hot stamped molded article becomes 700 MPa or more.
- the C content is less than 0.080%.
- the preferred C content is less than 0.075%, less than 0.070%, less than 0.060%, or less than 0.050%.
- Si 2.50% or less Si is an element contained as an impurity in steel.
- the Si content exceeds 2.50%, the weldability deteriorates and the transformation point becomes too high, and it becomes difficult to heat the steel sheet to a temperature higher than the transformation point in the heating process of the hot stamp. Therefore, the Si content is 2.50% or less.
- the preferred Si content is 2.00% or less, 1.50% or less, or 1.00% or less.
- the lower limit of the Si content is not particularly limited.
- the preferable Si content is 0.10% or more, 0.20% or more, or 0.30% or more.
- Mn 0.01% or more and less than 0.50%
- Mn is an element that degrades the thermal stability of a hot stamped molded article. In particular, when the Mn content is 0.50% or more, the thermal stability of the molded article after hot stamping is significantly degraded. Therefore, the Mn content is less than 0.50%.
- the Mn content is preferably less than 0.40%, less than 0.35%, less than 0.30%, or less than 0.25%.
- Mn is an element that combines with the impurity S to form MnS, and has the function of suppressing the adverse effect of S. In order to obtain this effect, the Mn content is made 0.01% or more.
- the Mn content is preferably 0.05% or more, 0.10% or more, or 0.15% or more.
- P 0.200% or less
- P is an element contained as an impurity in steel. If the P content exceeds 0.200%, the weldability and the toughness after hot stamping deteriorate significantly, so the P content is made 0.200% or less.
- the preferred P content is 0.100% or less, 0.050% or less, or 0.020% or less.
- the lower limit of the P content is not particularly limited, but excessive reduction of the P content causes an increase in steelmaking cost, and therefore, the P content is preferably 0.001% or more.
- P since P has the effect
- the preferable P content is 0.010% or more, 0.020% or more, or 0.030% or more.
- P content is 0.010% or more, 0.020% or more, or 0.030% or more.
- S 0.0200% or less
- S is an element contained as an impurity in steel to embrittle the steel. Therefore, the smaller the S content, the better, but if the S content exceeds 0.0200%, the adverse effect becomes particularly large, so the S content is made 0.0200% or less.
- the preferred S content is 0.0100% or less, 0.0050% or less, or 0.0030% or less. Although the lower limit of the S content is not particularly limited, excessively decreasing the S content causes an increase in steelmaking cost, so it is preferable to contain 0.0001% or more.
- Al 0.001 to 2.500%
- Al is an element having an action of deoxidizing molten steel. sol.
- the Al content is made 0.001% or more.
- the Al content is preferably 0.010% or more, 0.020% or more, or 0.040% or more. Meanwhile, sol. If the Al content is too high, the transformation point rises, and it becomes difficult to heat the steel sheet to a temperature above the transformation point in the heating process of the hot stamp. Therefore, sol.
- the Al content is at most 2.500%. sol.
- the Al content is preferably 1.000% or less, 0.500% or less, 0.100% or less, or 0.060% or less.
- N 0.0200% or less
- N is an element contained as an impurity in steel and forming nitride during continuous casting of steel. Since this nitride degrades the toughness after hot stamping, the lower the N content, the better. If the N content is more than 0.0200%, the adverse effect becomes particularly large, so the N content is made 0.0200% or less.
- the N content is preferably less than 0.0100%, less than 0.0080%, or less than 0.0050%.
- the lower limit of the N content is not particularly limited, but excessive reduction of the N content results in an increase in steelmaking cost, so it is preferable to contain N 0.001% or more.
- Cr 0.30% or more and less than 2.00% Cr is an element having an effect of improving the thermal stability of a hot stamped molded product (steel sheet after hot stamping) having a metal structure mainly composed of ferrite. .
- the Cr content is 0.30% or more.
- the Cr content is preferably 0.50% or more, 0.70% or more, or 0.90% or more.
- the Cr content is 2.00% or more, the volume fraction of martensite and / or bainite contained in the metal structure of the hot stamped molded product becomes excessive, and the thermal stability of the hot stamped molded product is degraded. . Therefore, the Cr content is less than 2.00%.
- the Cr content is preferably 1.50% or less, 1.20% or less, or 1.00% or less.
- the thermal stability of the hot stamped molded article is improved as the Mn content is lower and the Cr content is higher. Therefore, it is preferable to set the ratio ([Cr] / [Mn]) of the Cr content ([Cr]) to the Mn content ([Mn]) to 1.00 or more. More preferably, it is 1.05 or more, 1.50 or more, 2.50 or more, or 3.00 or more.
- Ti, Nb, V and Zr are elements having the function of increasing the tensile strength of the hot stamped molded product through the refinement of the metal structure. In order to obtain this effect, one or more selected from Ti, Nb, V and Zr may be contained as needed.
- the Ti content is more preferably 0.010% or more, and particularly preferably 0.020% or more.
- Nb is contained, the Nb content is more preferably 0.020% or more, and particularly preferably 0.030% or more.
- V is contained, the V content is more preferably 0.020% or more.
- Zr is contained, the Zr content is more preferably 0.010% or more.
- the Ti content is preferably less than 0.060%, more preferably less than 0.040%.
- the Nb content is preferably less than 0.060%, more preferably less than 0.040%.
- the V content is preferably less than 0.200%, more preferably less than 0.100%.
- the Zr content is preferably less than 0.200%, more preferably less than 0.100%.
- Mo 0 to 2.00%
- Cu 0 to 2.00%
- Ni 0 to 2.00%
- Mo, Cu and Ni have the effect of enhancing the tensile strength of the hot stamped molded product (steel plate after hot stamping). Therefore, one or more selected from Mo, Cu and Ni may be contained as needed.
- the preferable Mo content is 0.05% or more
- the preferable Cu content is 0.10% or more
- the preferable Ni content is 0.10% or more.
- the content of Mo, Cu and Ni exceeds 2.00%, respectively, the volume fraction of martensite and / or bainite contained in the metal structure of the molded article after hot stamping becomes excessive, resulting in a hot stamped article The thermal stability of the Therefore, even when it is contained, the contents of Mo, Cu and Ni are each 2.00% or less.
- the preferable Mo content is 0.50% or less
- the preferable Cu content is 1.00% or less
- the preferable Ni content is 1.00% or less.
- B 0 to 0.0200% B is an element which segregates at grain boundaries and improves the toughness of the steel sheet after hot stamping. In order to obtain this effect, it may be contained as needed.
- the B content is preferably 0.0001% or more.
- the B content is more preferably 0.0006% or more, still more preferably 0.0010% or more.
- the B content exceeds 0.0200%, the volume fraction of martensite and / or bainite contained in the metal structure of the hot stamped molded product becomes excessive, and the thermal stability of the hot stamped molded product is degraded. Therefore, even when it is contained, the B content is made 0.0200% or less.
- the B content is preferably 0.0050% or less, more preferably 0.0030% or less.
- Mg and REM are elements having the effect of improving the toughness after hot stamping by adjusting the shape of inclusions. Therefore, it may be contained as needed.
- the content of Ca or Mg is more than 0.0100%, or when the content of REM is more than 0.1000%, the effect is saturated and an excessive cost occurs. Therefore, even when it is contained, the content of each of Ca and Mg is 0.0100% or less, and the content of REM is 0.1000% or less.
- REM refers to a total of 17 elements of Sc, Y and lanthanoid, and the REM content means the total content of these elements.
- the lanthanoid is added industrially in the form of misch metal.
- Bi 0 to 0.0050%
- Bi is an element having an effect of improving toughness after hot stamping by refining the solidified structure. Therefore, it may be contained as needed.
- the Bi content is preferably 0.0001% or more.
- the Bi content is more preferably 0.0003% or more, still more preferably 0.0005% or more.
- the Bi content is made 0.0050% or less.
- the Bi content is preferably 0.0100% or less, more preferably 0.0050% or less.
- the balance is Fe and impurities.
- impurity is a component which is mixed due to various factors such as ore, scrap, etc. and various factors of the manufacturing process when industrially producing a steel plate, and is allowed within a range which does not adversely affect the present invention Means one.
- ⁇ Metallographic structure of hot stamped molded products The metal structure of the hot stamped molded article according to the present embodiment will be described. All or part of the hot stamped molded article according to the present embodiment has a metallographic structure including ferrite, martensite and bainite in the amounts shown below. In the following description of the metallographic structure, "%" means “% by volume”.
- the volume fraction of ferrite is made more than 60.0%.
- the volume fraction of ferrite is preferably more than 70.0%, more preferably more than 80.0%.
- the upper limit of the volume fraction of ferrite is not particularly limited, but is preferably less than 98.0%, more preferably less than 96.0%, in order to increase the strength of the hot stamped molded product. More preferably, it is less than 0%.
- the above-mentioned ferrite includes, in addition to polygonal ferrite, pseudo-polygonal ferrite and granular bainitic ferrite having a dislocation density higher than that of polygonal ferrite, and acicular ferrite having sawtooth-like grain boundaries.
- the ratio of polygonal ferrite to the entire ferrite is preferably 10.0% or more in volume ratio.
- Martensite 0% or more, less than 10.0% Bainite: 0% or more, less than 20.0%
- the volume fraction of martensite is less than 10.0%, and the volume fraction of bainite is less than 20.0%.
- the volume fraction of martensite is preferably less than 5.0%, more preferably less than 2.0%, and still more preferably less than 1.0%.
- the volume fraction of bainite is preferably less than 10.0%, more preferably less than 5.0%, and still more preferably less than 2.0%.
- the lower limit of the volume fraction of martensite and bainite is both 0%. However, since martensite and bainite have the effect of increasing the strength of the hot stamped molded product, they may be contained in the metal structure within the above range. If the volume fraction of martensite and bainite is less than 0.1%, the effect by the above-mentioned action can not be sufficiently obtained. Therefore, in the case of raising the strength, the lower limit value of the volume ratio of martensite and bainite is preferably 0.1% or more in each case, and more preferably 0.5% or more.
- the balance of the metallographic structure may contain pearlite or retained austenite, and may further contain precipitates such as cementite. Since it is not necessary to contain pearlite, retained austenite and precipitates, the lower limit of the volume fraction of pearlite, retained austenite and precipitates is all 0%.
- the volume ratio of pearlite is preferably 20.0% or less, more preferably 10.0% or less.
- the retained austenite has the effect of improving the impact absorption of the hot stamped part. Therefore, in order to obtain this effect, the volume fraction of retained austenite is preferably 0.5% or more, and more preferably 1.0% or more. On the other hand, when the retained austenite is excessively contained, the toughness after hot stamping is reduced. Therefore, the volume fraction of retained austenite is preferably 5.0% or less, more preferably 3.0% or less.
- the volume ratio of each metal structure is determined as follows. First, test pieces are taken from the hot stamped molded product, and after longitudinal cross section parallel to the rolling direction of the steel plate is polished, in the case of non-plated steel plate, 1/4 depth position of the plate thickness from the steel plate surface, plating In the case of a steel plate, the structure is observed at a 1/4 depth position of the plate thickness of the steel plate as the substrate from the boundary between the steel plate of the substrate and the plating layer.
- the hot stamped molded article includes a portion having a tensile strength of less than 700 MPa and a portion having a tensile strength of 700 MPa or more, the specimen is collected from a portion where the tensile strength is less than 700 MPa and observed. I do.
- the respective area ratios of ferrite and pearlite, bainite, martensite and retained austenite are obtained. Then, assuming that the area ratio is equal to the volume ratio, the measured area ratio is taken as the volume ratio of each tissue.
- the whole or a part of the hot stamped molded product according to the present embodiment has a tensile strength of less than 700 MPa in base steel plate. This is because when the tensile strength is 700 MPa or more, the thermal stability of the hot stamped molded product can not be secured.
- the tensile strength is less than 600 MPa, or less than 560 MPa.
- the tensile strength of the hot stamped molded article is preferably 440 MPa or more, and more preferably 490 MPa or more.
- a soft part having a tensile strength of less than 700 MPa and a hard part having a tensile strength of 700 MPa or more may be mixed in the molded product.
- the reduction in tensile strength ( ⁇ TS) with respect to the tensile strength before hot stamping is 100 MPa or less when heat treatment is performed at 170 ° C. for 20 minutes.
- the ⁇ TS is preferably 60 MPa or less, more preferably 30 MPa or less.
- the reason for the decrease in strength at the time of paint baking is that fine iron carbide or fine iron carbon clusters present in ferrite are coarse iron by heat treatment at the time of paint baking. It is believed that this is to change to carbides.
- ⁇ TS tensile strength after heat treatment at 170 ° C. for 20 minutes. It can be evaluated indirectly by ⁇ TS). If ⁇ TS is 100 MPa or less, the formation of fine iron carbides or fine iron carbon clusters in ferrite is suppressed, and it is judged that the thermal stability is excellent.
- the hot stamped molded article according to the present embodiment may have a plating layer on the surface.
- the plating layer By providing the plating layer on the surface, it is possible to prevent the formation of scale at the time of hot stamping, and to further improve the corrosion resistance of the hot stamped molded product.
- the type of plating is not particularly limited as long as it meets the purpose.
- the plated layer of the hot stamped molded product can be formed by hot stamping using a plated steel plate as described later.
- As a kind of plating layer the zinc-based plating layer and the aluminum-based plating layer which were hot-stamped using the zinc-based plating steel plate and the aluminum-based plating steel plate are illustrated.
- the steel plate for hot stamping suitable for manufacturing said hot stamped molded article is demonstrated.
- the chemical composition of the hot stamping steel sheet has the same chemical composition as the above-described hot stamped molded product because the chemical composition is not substantially changed by the hot stamping.
- the metallographic structure of the steel plate for hot stamping according to the present embodiment contains iron carbide, and the chemical composition of iron carbide (Mn content in iron carbide and Cr content) satisfies the following equation (i). [Mn] ⁇ + [Cr] ⁇ > 2.5 (i) However, the meaning of each symbol in the above formula is as follows. [Mn] ⁇ : Mn content in iron carbide (atomic%), where the total content of Fe, Mn and Cr contained in iron carbide is 100 atomic% [Cr] ⁇ : Cr content in iron carbide (atomic%), where the total content of Fe, Mn and Cr contained in iron carbide is 100 atomic%
- the left side value of said Formula (i) is more than 3.0, and it is more preferable that it is more than 4.0.
- the left side value of the formula (i) is preferably less than 30.0, and more preferably less than 20.0.
- the chemical composition of iron carbide is measured by the following procedure. First, test pieces are collected from arbitrary positions of the steel plate, and a longitudinal cross section parallel to the rolling direction of the steel plate is polished, and then precipitates are extracted from the surface of the steel plate by a replica method at a 1/4 depth position of the plate thickness. The precipitate is observed using a transmission electron microscope (TEM), and identification and composition analysis of the precipitate are performed by electron diffraction and energy dispersive X-ray analysis (EDS).
- TEM transmission electron microscope
- EDS energy dispersive X-ray analysis
- Quantitative analysis of iron carbides by EDS is performed for three elements of Fe, Mn and Cr, and the Mn content (atomic%) and the Cr content (atomic%) when the total content of them is 100 atomic% , respectively obtained as [Mn] theta and [Cr] theta.
- This quantitative analysis is performed on a plurality of iron carbides, and the average value thereof is taken as the Mn content and the Cr content in iron carbides in the steel sheet.
- the number of iron carbides to be measured is 10 or more, and the larger the number of measurements, the better.
- the iron carbide includes cementite which exists in isolation in the metal structure, in addition to cementite which constitutes pearlite.
- a 1/4 depth position of the plate thickness from the steel plate surface in the case of a hot-rolled annealed steel plate, a cold-rolled steel plate or an annealed steel plate, a 1/4 depth position of the plate thickness from the steel plate surface.
- the above-described metallographic structure is defined at a 1/4 depth position of the thickness of a steel plate which is a steel.
- the volume fraction of iron carbide does not need to be determined in particular, but in order to refine the metal structure after hot stamping and increase the tensile strength, the volume fraction of iron carbide is preferably 1% or more, and 3% or more It is more preferable to On the other hand, when the volume fraction of iron carbide is excessive, the tensile strength of the steel sheet after hot stamping becomes too high and the thermal stability is impaired. Therefore, the volume fraction of iron carbide is preferably 20% or less, and more preferably 15% or less.
- the remainder of the metallographic structure of the steel plate for hot stamping according to this embodiment is mainly composed of ferrite, but may contain martensite, tempered martensite, bainite and retained austenite, and further, precipitates other than iron carbides May be included.
- martensite, tempered martensite, bainite and retained austenite deteriorate the toughness after hot stamping, so the volume fraction of these structures is preferably as low as possible.
- the volume fraction of martensite, tempered martensite, bainite and retained austenite is preferably less than 1.0%, and more preferably less than 0.5%.
- the volume fraction in the metallographic structure of the steel plate for hot stamping can be determined by the same method as in the case of the hot stamped steel.
- the method of manufacturing a hot stamped molded product according to the present embodiment comprises the steps of heating a steel plate for hot stamping having the above-described chemical composition and metal structure, and performing hot stamping on the heated steel plate for hot stamping, including. In the hot stamping process, mold cooling and molding are performed to obtain a hot stamped article.
- the heating temperature T (° C.) be higher than Ac 1 point.
- the Ac 1 point is a temperature at which austenite begins to form in the metal structure when the base steel plate is heated, and can be obtained from the thermal expansion change of the steel plate in the heating step.
- the heating temperature is increased, the dissolution of carbides is promoted and the strength of the hot stamped molded article is increased.
- the tensile strength of the hot stamped molded article is set to 440 MPa or more, the heating temperature is set to Ac 1 point or more.
- the heating temperature should be above the Ac 3 point.
- the Ac 3 point is a temperature at which the ferrite disappears in the metal structure when the steel plate to be subjected to the hot stamping is heated, and can be obtained from the thermal expansion change of the steel plate in the heating step.
- the upper limit of the heating temperature is not particularly limited, but if the heating temperature is too high, austenite is coarsened, and the strength of the hot stamped molded article is lowered. Therefore, the heating temperature is preferably 1000 ° C. or less, more preferably 950 ° C. or less, and still more preferably 900 ° C. or less.
- the starting temperature of the hot stamping is preferably (T-300) ° C. or higher, where T (° C.) is the heating temperature.
- T (° C.) is the heating temperature.
- the hot stamp initiation temperature is increased, the re-deposition of carbides that occur before the hot stamp initiation is suppressed, and the strength of the hot stamped molded article is increased.
- the start temperature of the hot stamp is set to (T-300) ° C. or more.
- the starting temperature of the hot stamp is Ar More than 3 points are preferable.
- the Ar 3 point is a temperature at which ferrite starts to form in the metallographic structure when the base steel sheet is cooled, and is obtained from the thermal expansion change when the steel sheet is cooled after the heating step.
- another manufacturing method of the hot stamped molded product according to the present embodiment is a bonding step of bonding a steel plate (steel plate for hot stamp) having the above-mentioned chemical composition and metal composition to a steel plate for bonding to make a bonded steel plate And heating the bonded steel sheet and then hot stamping the heated bonded steel sheet.
- a steel plate steel plate for hot stamp
- the steel plate for joining can be joined by welding.
- T (° C.) of the joined steel sheet above Ac 1 point of the steel plate for hot stamping
- start temperature of the hot stamp T-300 ° C. or higher.
- a more preferable heating temperature in this case is more than Ac 3 point of the steel plate, and more preferable starting temperature of the hot stamp is more than Ar 3 point of the steel plate. The reason is the same as in the case where the bonding step is not included.
- the tensile strength after hot stamping is preferably 700 MPa or more. Further preferred tensile strength after hot stamping is more than 1000 MPa, more than 1200 MPa or more than 1500 MPa.
- the C content of the steel plate for joining is preferably 0.080% or more.
- the lower limit of the preferable C content is 0.100%, 0.120%, or 0.200%.
- the Mn content of the steel plate for bonding is preferably 0.50% or more.
- the lower limit of the preferred Mn content is 0.80%, 1.00%, or 1.20%.
- the hot-rolled sheet annealing is given to the steel plate (steel plate for hot stamps) used as said raw material so that it may mention later.
- cold rolling or cold rolling and annealing may be further performed.
- a steel plate for joining a hot rolled steel plate, a cold rolled steel plate obtained by cold rolling the hot rolled steel plate, a hot rolled annealed steel plate obtained by annealing the hot rolled steel plate, and a cold rolled steel obtained by annealing the cold rolled steel plate It may be any of the annealed steel plates.
- the plated steel plate by which plating was given to the surface for the steel plate for hot stamps, and the steel plate for joining.
- the type of the plated steel sheet is not particularly limited.
- hot-dip galvanized steel sheet, alloyed galvanized steel sheet, hot-dip aluminized steel sheet, hot-dip Zn-Al alloy coated steel sheet, hot-dip Zn-Al-Mg alloy plated steel sheet, hot-dip Zn-Al- Examples include Mg-Si alloy plated steel sheet, electrogalvanized steel sheet, and electric Ni-Zn alloy plated steel sheet.
- Method of manufacturing steel plate for hot stamping In the method of manufacturing a steel plate for hot stamping according to the present embodiment, after hot rolling is performed on a slab having the above-described chemical composition, the steel sheet is hot rolled into a hot rolled steel sheet in a temperature range of 800 ° C. or less It includes a rolling process and a hot-rolled sheet annealing process of applying hot-rolled sheet annealing which heats the hot-rolled steel sheet to a temperature range exceeding 650 ° C. to obtain a hot-rolled annealed steel sheet.
- the coiling temperature after hot rolling is set to 800 ° C. or less. If the winding temperature is higher than 800 ° C., the metallographic structure of the hot-rolled steel sheet becomes excessively coarse, and the tensile strength of the steel sheet after hot stamping decreases.
- the winding temperature is preferably less than 650 ° C., more preferably less than 600 ° C., still more preferably less than 550 ° C.
- the hot-rolled and wound steel sheet is subjected to a treatment such as degreasing according to a known method, if necessary, and then annealed.
- the annealing applied to the hot rolled steel sheet is called hot rolled sheet annealing, and the steel sheet after hot rolled sheet annealing is called hot rolled annealed steel sheet.
- descaling may be performed by pickling or the like.
- the heating temperature in a hot-rolled sheet annealing process shall be 650 degreeC or more. This is to increase the Mn content and the Cr content in iron carbide in the metal structure of the hot-rolled and annealed steel sheet. It is preferable that the heating temperature in a hot-rolled sheet annealing process is 680 degreeC or more, and it is more preferable that it is 700 degreeC or more. On the other hand, if the heating temperature in the hot-rolled sheet annealing step becomes too high, the metallographic structure of the hot-rolled annealed steel sheet becomes coarse, and the tensile strength after hot stamping decreases. Therefore, the upper limit of the heating temperature in the hot-rolled sheet annealing step is preferably less than 750 ° C., and more preferably less than 720 ° C.
- a steel having the above-described composition is melted by a known means and then made into a steel ingot by a continuous casting method or a steel ingot by any casting method After that, it is made into a steel piece by a method such as slab rolling.
- a method such as slab rolling.
- the continuous casting step in order to suppress the generation of surface defects caused by inclusions, it is preferable to cause the molten steel to generate an additional external flow such as electromagnetic stirring in the mold.
- the ingot or billet may be reheated after being cooled and subjected to hot rolling, and the ingot at high temperature after continuous casting or the billet in high temperature after rolled is as it is Alternatively, it may be subjected to hot rolling with keeping warm or performing additional heating.
- such steel ingots and billets are collectively referred to as “slab” as a material for hot rolling.
- the temperature of the slab to be subjected to hot rolling is preferably less than 1250 ° C., more preferably less than 1200 ° C., in order to prevent austenite coarsening.
- Hot rolling is preferably completed in a temperature range of Ar 3 points or more in order to refine the metal structure of the hot rolled steel sheet by transforming austenite after completion of rolling.
- the rough rolled material When hot rolling consists of rough rolling and finish rolling, the rough rolled material may be heated between rough rolling and finish rolling in order to complete finish rolling at the above temperature. Under the present circumstances, it is desirable to suppress the fluctuation
- a method of heating the rough rolled material may be performed using a known means.
- a solenoid induction heating device is provided between the rough rolling mill and the finishing rolling mill, and the heating temperature rise amount is controlled based on the temperature distribution in the longitudinal direction of the rough rolling material on the upstream side of this induction heating device. May be
- the hot-rolled annealed steel sheet may be cold-rolled to form a cold-rolled steel sheet.
- Cold rolling may be performed according to a conventional method, and descaling may be performed by pickling or the like before cold rolling.
- the cold pressure ratio (cumulative rolling reduction in cold rolling) to 30% or more, and 40% or more Is more preferred. If the cold pressure rate is too high, the toughness after hot stamping deteriorates, so the cold pressure rate is preferably 60% or less, more preferably 50% or less.
- the cold pressure ratio is preferably 60% or more, and more preferably 70% or more.
- the cold rolled steel sheet may be annealed to form an annealed steel sheet.
- Annealing may be performed according to a conventional method, and prior to annealing, treatment such as degreasing may be performed by a known method.
- the lower limit value of the soaking temperature in annealing is preferably set to 600 ° C., 650 ° C., or 700 ° C.
- the soaking temperature in annealing should be 800 ° C. or less or 760 ° C. or less because the grain structure of the annealed steel sheet becomes coarse due to grain growth.
- the soaking time is preferably less than 300 seconds, or less than 120 seconds.
- the annealing may be performed by either box annealing or continuous annealing, but continuous annealing is preferable from the viewpoint of productivity.
- the hot rolled annealed steel plate, the cold rolled steel plate and the annealed steel plate thus obtained may be subjected to temper rolling according to a conventional method.
- the steel plate for hot stamping may have a plating layer on the surface layer for the purpose of preventing formation of scale at hot stamping and corrosion resistance improvement of the steel plate after hot stamping.
- the type of plating is not particularly limited as long as it is suitable for the above purpose, and is not particularly limited.
- hot-dip galvanized steel sheet, alloyed galvanized steel sheet, hot-dip aluminum plated steel sheet, hot-dip Zn-Al alloy plated steel sheet, hot-dip Zn-Al- Examples thereof include Mg alloy plated steel sheets, hot-dip Zn-Al-Mg-Si alloy plated steel sheets, electrogalvanized steel sheets, and electric Ni-Zn alloy plated steel sheets.
- the hot-rolled annealed steel sheet, the cold-rolled steel sheet or the annealed steel sheet manufactured by the method described above may be used as a base steel sheet and plating may be performed according to a conventional method.
- the lower limit value of the soaking temperature in the annealing process of continuous hot-dip plating is set to 600 ° C., 650 ° C. or 700 ° C. in order to refine the metal structure of the plated steel sheet by recrystallization. Is preferred.
- the soaking temperature is too high, the metallographic structure of the annealed steel sheet becomes coarse due to grain growth, so the upper limit value of the soaking temperature in the annealing process of continuous hot-dip plating is 800 ° C or It is preferable to set it as 760 degreeC. After hot-dip plating, the steel sheet may be reheated to be alloyed.
- an electroplated steel sheet In the case of producing an electroplated steel sheet, a hot-rolled annealed steel sheet, a cold-rolled steel sheet or an annealed steel sheet manufactured by the above-described method is used as a base steel sheet, and a known pretreatment for surface cleaning and adjustment is performed as needed. After application, electroplating may be performed according to a conventional method. The plated steel sheet obtained in this manner may be subjected to temper rolling according to a conventional method.
- Example 1 Molten steel was cast using a vacuum melting furnace to produce steels AR having the chemical compositions shown in Table 1.
- the Ac 1 point and Ac 3 point in Table 1 were determined from the thermal expansion change when the cold rolled steel plates of steels AR were heated at 2 ° C./sec.
- the Ar 3 point in Table 1 was determined from the thermal expansion change when the cold rolled steel plates of steels A to M were heated to 950 ° C. and then cooled at 10 ° C./sec.
- the steels A to R were heated to 1200 ° C. and held for 60 minutes, and then hot rolling was performed under the hot rolling conditions shown in Table 2.
- the steels A to R are subjected to 10 passes of rolling in a temperature range of Ar 3 points or more to form hot-rolled steel plates having a thickness of 2.0 to 3.6 mm.
- the hot rolled steel sheet is cooled to 490 to 600 ° C. by water spray, the cooling end temperature is taken as the winding temperature, and the hot rolled steel plate is inserted into the electrically heated furnace maintained at this winding temperature.
- the hot rolled steel sheet was furnace cooled to room temperature at an average cooling rate of 20 ° C./hour to simulate slow cooling after winding.
- Hot rolled sheet annealing was performed on a part of the hot rolled steel sheet after slow cooling. Specifically, the heat-rolled steel plate is heated to 620 to 710 ° C. at an average heating rate of 50 ° C./hour using an electric heating furnace, and then held for 1 hour, followed by cooling at an average cooling rate of 20 ° C./hour. It was set as a hot-rolled annealing steel plate.
- the hot rolled steel plate and the hot rolled annealed steel plate except test number 3 were pickled and used as a base material for cold rolling, and cold rolled at a rolling reduction of 61% to obtain a cold rolled steel plate having a thickness of 1.4 mm. .
- a portion of the cold-rolled steel plate was heated to 750 ° C. at a mean heating rate of 10 ° C./s and soak for 60 seconds using a continuous annealing simulator. Then, after cooling to 400 degreeC and hold
- a part of the cold rolled steel plate was heated to the soaking temperature for annealing shown in Table 2 at an average heating rate of 10 ° C./sec using a hot-dip plating simulator and homogenized for 60 seconds. Subsequently, the base steel sheet was cooled, immersed in a hot dip galvanizing bath or a hot dip aluminum plating bath, and hot dip galvanizing or hot dip aluminum plating was applied. After hot-dip galvanizing, some base steel plates were heated to 520 ° C. to be alloyed.
- the hot-rolled steel plate, the hot-rolled annealed steel plate, the cold-rolled steel plate, the hot-dip galvanized steel plate, the alloyed hot-dip galvanized steel plate, and the hot-dip aluminized steel plate (these steel plates are collectively called hot From the steel sheet for stamping), the test piece for structure observation was extract
- JIS 13 B tensile test specimens were taken from the above steel plate for hot stamping along the direction orthogonal to the rolling direction, and a tensile test was conducted at a tensile speed of 10 mm / min to determine the tensile strength.
- Table 3 shows the results of observation of the metal structure of the steel plate for hot stamping and the results of investigation of the mechanical properties of the steel plate for hot stamping.
- a base plate for hot stamping having a width of 240 mm and a length of 170 mm was collected, and a hat member having a shape shown in FIG. 1 was manufactured by hot stamping.
- the base plate was heated at the heating temperature shown in Table 4 for 4 minutes using a gas heating furnace, then taken out from the heating furnace, allowed to cool, and equipped with a cooling device at the starting temperature shown in Table 4. It was sandwiched between molds and hat-shaped.
- a heat treatment was performed on a part of the obtained hat member (hot stamped molded article) at 170 ° C. for 20 minutes using an electric heating furnace.
- the longitudinal section is subjected to nital corrosion and repeller corrosion,
- a plated steel plate it is 1/4 depth position of the thickness of the steel plate from the surface of the steel plate.
- a plated steel plate it is 1/4 deep of the thickness of the steel plate which is a substrate from the boundary between the steel plate and the plating layer.
- the metallographic structure in the vertical position was observed.
- the area ratio of ferrite, martensite, bainite and pearlite was measured by image processing, and this was defined as the volume ratio.
- JIS 13 B tensile test specimens were taken from the punch bottom of the hat member before and after heat treatment along the longitudinal direction of the member, and a tensile test was performed at a tensile speed of 10 mm / min to determine the tensile strength.
- the difference ( ⁇ TS) between the tensile strength of the hat member not subjected to the heat treatment and the tensile strength of the hat member subjected to the heat treatment is determined, and if ⁇ TS is 100 MPa or less, the thermal stability of the hat member is good. It was judged.
- Table 4 shows the result of observing the metal structure of the hat member and the result of evaluating the mechanical properties of the hat member.
- the underlined numerical values mean that they are out of the scope of the present invention.
- test numbers 1 to 15, 19 to 23, 27, 29, 31 satisfying the definition of the present invention are all good because the TS of the hot stamped molded article is less than 700 MPa and the ⁇ TS is 100 MPa or less. It shows thermal stability.
- the test number is 1 to 4, 7 to 9, 11 to 13, 15, 19 in which the temperature is higher than Ac 1 and the hot stamping start temperature is (heating temperature -300) ° C or higher.
- the tensile strengths of the hot stamped molded articles of -23, 27, 29, 31 were 440 MPa or more, and the strength characteristics were particularly good.
- test numbers 16 to 18 and 24 to 26 of the comparative examples using the steel plate whose chemical composition is out of the range of the present invention and / or the steel plate for hot stamping used did not have a preferable structure.
- the TS of the hot stamped molded product is 700 MPa or more and the ⁇ TS is 100 MPa or more, or the ⁇ TS is 100 MPa or more, and the thermal stability is inferior.
- the C content of the steel is too high, so the volume fraction of martensite is excessive in the metal structure of the hot stamped molded article, and the tensile strength of the hot stamped article is It was 700 MPa or more, and ⁇ TS was large.
- Test No. 17 using steel F had a tensile strength of 700 MPa or more and a large ⁇ TS, because the Mn content of the steel was too high.
- the test No. 18 using steel G had a tensile strength of 700 MPa or more and a large ⁇ TS, because the Cr content of the steel was too low.
- Test Nos. 24 and 25 using steel M have too high a Cr content of the steel, so the volume fraction of martensite is excessive in the metal structure of the hot stamped molded product, and the tensile strength of the hot stamped molded product is 700 MPa or more There was a large ⁇ TS.
- test numbers 32 and 33 using steel Q had large ⁇ TS because the Mn content of the steel was too high.
- the chemical compositions are within the scope of the present invention, the test numbers 26, 28 and 30 of the comparative examples using steel plates in which the metallographic structure of the steel plate for hot stamping deviates from the scope of the present invention Of 100 MPa or more, and thermal stability was inferior.
- test number 26 using steel N and test number 30 using steel P did not perform hot-rolled sheet annealing, Mn in iron carbides in the metallographic structure of the steel plate for hot stamping The sum of the content and the Cr content was low, and ⁇ TS was large.
- Test No. 28 using steel O has a low sum of Mn content and Cr content in iron carbide in the metal structure of the steel plate for hot stamping because the heating temperature in the hot-rolled sheet annealing step is too low. It was great.
- Example 2 Molten steel was cast using a vacuum melting furnace, and in Example 1, steels A to C having the chemical compositions shown in Table 1 were produced. Hot rolling, hot-rolled sheet annealing, cold rolling, and annealing are performed using steels A to C under the conditions shown in Table 5 as in Example 1, and then a plating treatment is performed, and a galvanized steel sheet is produced. , An alloyed galvanized steel sheet, and a hot-dip aluminum-plated steel sheet (steel sheet for hot stamping) were manufactured.
- Table 6 shows the results of observation of the metal structure of the steel plate for hot stamping and the results of investigation of the mechanical properties of the steel plate for hot stamping.
- a hot stamping base plate having a thickness of 1.4 mm, a width of 240 mm and a length of 170 mm was collected.
- the base plate was joined with a joining steel plate of the same size by laser welding to produce a joined steel plate having a thickness of 1.4 mm, a width of 240 mm, and a length of 340 mm.
- the chemical composition is mass%, and 0.21% C-0.13% Si-1.31% Mn-0.012% P-0.0018% S-0.043% sol.
- a cold rolled steel sheet of Al-0.0030% N-0.21% Cr-0.0018% B was used.
- the bonded steel plates were hot-stamped in the same manner as in Example 1 under the conditions shown in Table 7 to produce a hat member having a shape shown in FIG. Thereafter, a part of the obtained hat member was subjected to heat treatment at 170 ° C. for 20 minutes using an electric heating furnace.
- Example 7 shows the result of observing the metal structure of the hat member (hot stamped molded product) and the result of evaluating the mechanical characteristics of the hat member.
- the TS of the hot stamped molded article is less than 700 MPa, and the ⁇ TS is 100 MPa or less, which indicates good thermal stability.
- the metallographic structure of the joining steel plate portion of the hat member was a single structure of martensite, and the tensile strength was 1588 MPa.
- thermo stability having a portion with a small variation in strength due to the coating baking treatment and a tensile strength of less than 700 MPa.
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Abstract
Description
本願は、2017年10月02日に、日本に出願された特願2017-193095号に基づき優先権を主張し、その内容をここに援用する。
具体的には、特許文献7には、C含有量を低めにするとともに焼入れ元素を一定量以上含有させ、冷却中にフェライト、パーライトおよびマルテンサイトの形成を抑制した600~1200MPa級自動車用高強度部材およびその製造方法が開示されている。また、特許文献8には、C含有量を低めに制限するとともにTiを含有させ、マルテンサイトの生成量を制御した、引張強さが500MPa以上のホットスタンプ部材とその製造方法が開示されている。
(2)上記(1)に記載のホットスタンプ成形品では、前記化学組成が、質量%で、Ti:0.001~0.300%、Nb:0.001~0.300%、V:0.001~0.300%、および、Zr:0.001~0.300%、から選択される1種以上を含有してもよい。
(3)上記(1)または(2)に記載のホットスタンプ成形品は、前記化学組成が、質量%で、Mo:0.001~2.00%、Cu:0.001~2.00%、および、Ni:0.001~2.00%、から選択される1種以上を含有してもよい。
(4)上記(1)~(3)のいずれかに記載のホットスタンプ成形品は、前記化学組成が、質量%で、B:0.0001~0.0200%を含有してもよい。
(5)上記(1)~(4)のいずれかに記載のホットスタンプ成形品は、前記化学組成が、質量%で、Ca:0.0001~0.0100%、Mg:0.0001~0.0100%、および、REM:0.0001~0.1000%、から選択される1種以上を含有してもよい。
(6)上記(1)~(5)のいずれかに記載のホットスタンプ成形品は、前記化学組成が、質量%で、Bi:0.0001~0.0500%、を含有してもよい。
(7)上記(1)~(6)のいずれかに記載のホットスタンプ成形品は、表面にめっき層を有してもよい。
(8)本発明の別の態様に係るホットスタンプ用鋼板は、化学組成が、質量%で、C:0.001%以上0.080%未満、Si:2.50%以下、Mn:0.01%以上0.50%未満、P:0.200%以下、S:0.0200%以下、sol.Al:0.001~2.500%、N:0.0200%以下、Cr:0.30%以上2.00%未満、Ti:0~0.300%、Nb:0~0.300%、V:0~0.300%、Zr:0~0.300%、Mo:0~2.00%、Cu:0~2.00%、Ni:0~2.00%、B:0~0.0200%、Ca:0~0.0100%、Mg:0~0.0100%、REM:0~0.1000%、Bi:0~0.0500%、残部:Feおよび不純物であり、金属組織が、鉄炭化物を含み、前記鉄炭化物中のMn含有量及びCr含有量が下記(i)式を満足する。
[Mn]θ+[Cr]θ>2.5 ・・・(i)
但し、上記式中の各記号の意味は以下のとおりである。
[Mn]θ:鉄炭化物に含まれるFe、MnおよびCrの合計含有量を100原子%としたときの、原子%での鉄炭化物中のMn含有量
[Cr]θ:前記鉄炭化物に含まれるFe、MnおよびCrの合計含有量を100原子%としたときの、原子%での鉄炭化物中のCr含有量
(9)上記(8)に記載のホットスタンプ用鋼板は、前記化学組成が、質量%で、Ti:0.001~0.300%、Nb:0.001~0.300%、V:0.001~0.300%、および、Zr:0.001~0.300%、から選択される1種以上を含有してもよい。
(10)上記(8)または(9)に記載のホットスタンプ用鋼板は、前記化学組成が、質量%で、Mo:0.001~2.00%、Cu:0.001~2.00%、および、Ni:0.001~2.00%、から選択される1種以上を含有してもよい。
(11)上記(8)~(10)のいずれかに記載のホットスタンプ用鋼板は、前記化学組成が、質量%で、B:0.0001~0.0200%、を含有してもよい。
(12)上記(8)~(11)のいずれかに記載のホットスタンプ用鋼板は、前記化学組成が、質量%で、Ca:0.0001~0.0100%、Mg:0.0001~0.0100%、および、REM:0.0001~0.1000%、から選択される1種以上を含有してもよい。
(13)上記(8)~(12)のいずれかに記載のホットスタンプ用鋼板は、前記化学組成が、質量%で、Bi:0.0001~0.0500%、を含有してもよい。
(14)上記(8)~(13)のいずれかに記載のホットスタンプ用鋼板は、表面にめっき層を有してもよい。
(15)本発明の別の態様に係るホットスタンプ成形品の製造方法は、上記(1)~(6)のいずれかに記載のホットスタンプ成形品を製造する方法であって、(8)~(13)のいずれかに記載のホットスタンプ用鋼板を加熱温度T℃まで加熱する加熱工程と、前記加熱工程後の前記ホットスタンプ用鋼板に対してホットスタンプを行うホットスタンプ工程と、を備える。
(16)本発明の別の態様に係るホットスタンプ成形品の製造方法は、上記(1)~(6)のいずれかに記載のホットスタンプ成形品を製造する方法であって、(8)~(13)のいずれかに記載のホットスタンプ用鋼板を、接合用鋼板と接合して接合鋼板とする接合工程と、前記接合工程後の接合鋼板を加熱温度T℃まで加熱する加熱工程と、前記加熱工程後の前記接合鋼板に対してホットスタンプを行うホットスタンプ工程と、を備える。
(17)本発明の別の態様に係るホットスタンプ成形品の製造方法は、上記(7)に記載のホットスタンプ成形品を製造する方法であって、(14)に記載のホットスタンプ用鋼板を加熱温度T℃まで加熱する加熱工程と、前記加熱工程後の前記ホットスタンプ用鋼板に対してホットスタンプを行うホットスタンプ工程と、を備える。
(18)本発明の別の態様に係るホットスタンプ成形品の製造方法は、上記(7)に記載のホットスタンプ成形品を製造する方法であって、(14)に記載のホットスタンプ用鋼板を、接合用鋼板と接合して接合鋼板とする接合工程と、前記接合工程後の接合鋼板を加熱温度T℃まで加熱する加熱工程と、前記加熱工程後の前記接合鋼板に対してホットスタンプを行うホットスタンプ工程と、を備える。
(19)上記(15)~(18)のいずれかに記載のホットスタンプ成形品の製造方法は、前記加熱工程において、前記加熱温度T℃が、前記ホットスタンプ用鋼板のAc1点を超える温度であり、前記ホットスタンプ工程において、ホットスタンプ開始温度が(T-300)℃以上の温度であってもよい。
(20)本発明の別の態様に係るホットスタンプ用鋼板の製造方法は、(8)~(14)のいずれかに記載のホットスタンプ用鋼板を製造する方法であって、化学組成が、質量%で、C:0.001%以上0.080%未満、Si:2.50%以下、Mn:0.01%以上0.50%未満、P:0.200%以下、S:0.0200%以下、sol.Al:0.001~2.500%、N:0.0200%以下、Cr:0.30%以上2.00%未満、Ti:0~0.300%、Nb:0~0.300%、V:0~0.300%、Zr:0~0.300%、Mo:0~2.00%、Cu:0~2.00%、Ni:0~2.00%、B:0~0.0200%、Ca:0~0.0100%、Mg:0~0.0100%、REM:0~0.1000%、Bi:0~0.0500%、残部:Feおよび不純物であるスラブに対して、熱間圧延を施した後、800℃以下の温度域で巻取って熱延鋼板とする熱間圧延工程と、前記熱延鋼板に650℃を超える温度域まで加熱する熱延板焼鈍を施して熱延焼鈍鋼板とする熱延板焼鈍工程と、を備える。
(21)上記(20)に記載のホットスタンプ用鋼板の製造方法は、さらに、前記熱延板焼鈍工程後の前記熱延焼鈍鋼板に、任意に、冷間圧延、及び焼鈍のいずれかまたは両方を行った後、めっきを行うめっき工程を備えてもよい。
この理由は明らかではないが、(a)Mn含有量が過剰であると、オーステナイトからフェライトへの変態温度が低下し、ホットスタンプ後の冷却過程において、フェライト中に微細な鉄炭化物または微細な鉄炭素クラスターが生成し、フェライトが硬質化すること、(b)Crを含有させ、鉄炭化物中のMn含有量、Cr含有量を一定以上とすることで鉄炭化物が安定化し、フェライト中における微細な鉄炭化物または微細な鉄炭素クラスターの生成が抑制されること、および(c)フェライト中に存在する微細な鉄炭化物または微細な鉄炭素クラスターは、塗装焼付時の熱処理により粗大な鉄炭化物に変化し、フェライトの強度が低下すること、に起因すると推定される。
以下、本発明の一実施形態に係るホットスタンプ成形品(本実施形態に係るホットスタンプ成形品)、及びその素材として好適なホットスタンプ用鋼板(本実施形態に係るホットスタンプ用鋼板)、ならびにそれらの製造方法の各要件について詳しく説明する。
本実施形態に係るホットスタンプ成形品の全部または一部は、以下に示す化学組成を有する。各元素の限定理由は下記のとおりである。以下の説明において含有量についての「%」は、「質量%」を意味する。ホットスタンプ成形品が、700MPa未満の引張強さを有する部分と、700MPa以上の引張強さを有する部分とを備えている場合、少なくとも引張強さが700MPa未満となる部分が以下の化学組成を有していればよい。
Cは、ホットスタンプ後の鋼板(ホットスタンプ成形品が備える鋼板)の引張強さを上昇させる効果を有する元素である。C含有量が0.001%未満では、ホットスタンプによる引張強さの上昇が望めない。好ましいC含有量は0.010%以上、0.020%以上、または0.030%以上である。
一方、C含有量が0.080%以上であると、ホットスタンプ後の金属組織においてマルテンサイトおよび/またはベイナイトの体積率が増加して、ホットスタンプ成形品の引張強さが700MPa以上となる。この場合、後述するようにMnおよびCr含有量を調整しても、ホットスタンプ成形品の熱的安定性を確保することができなくなる。したがって、C含有量は0.080%未満とする。好ましいC含有量は0.075%未満、0.070%未満、0.060%未満、または0.050%未満である。
Siは、鋼中に不純物として含有される元素である。Si含有量が2.50%を超えると、溶接性が劣化するとともに、変態点が高くなりすぎ、ホットスタンプの加熱過程で変態点以上の温度に鋼板を加熱することが困難となる。そのため、Si含有量は2.50%以下とする。好ましいSi含有量は2.00%以下、1.50%以下、または1.00%以下である。ホットスタンプ用鋼板としてめっき鋼板を用いる場合は、めっき性を確保するためにSi含有量を0.50%未満とすることが好ましく、0.40%未満とすることがより好ましい。
Si含有量の下限は特に限定しないが、Si含有量を過度に低下させることは製鋼コストの上昇を招くため、Siを0.001%以上含有させることが好ましい。また、Siは、ホットスタンプ後の鋼板の引張強さを高める作用を有するので、積極的に含有させてもよい。高強度化の観点からは、好ましいSi含有量は0.10%以上、0.20%以上、または0.30%以上である。
Mnは、ホットスタンプ成形品の熱的安定性を劣化させる元素である。特に、Mn含有量が0.50%以上であると、ホットスタンプ後の成形品の熱的安定性が著しく劣化する。したがって、Mn含有量は0.50%未満とする。Mn含有量は好ましくは0.40%未満、0.35%未満、0.30%未満、または0.25%未満である。
一方、Mnは、不純物であるSと結合してMnSを形成し、Sによる弊害を抑制する作用を有する元素である。この効果を得るため、Mn含有量は0.01%以上とする。Mn含有量は好ましくは0.05%以上、0.10%以上、または0.15%以上である。
Pは、鋼中に不純物として含有される元素である。P含有量が0.200%を超えると溶接性およびホットスタンプ後の靭性が著しく劣化するため、P含有量は0.200%以下とする。好ましいP含有量は0.100%以下、0.050%以下、または0.020%以下である。
P含有量の下限は特に限定しないが、P含有量を過度に低下させることは製鋼コストの上昇を招くため、0.001%以上含有させることが好ましい。また、Pは、ホットスタンプ後の成形品の引張強さを高める作用を有するので、積極的に含有させてもよい。高強度化の観点からは、好ましいP含有量は0.010%以上、0.020%以上、または0.030%以上である。ホットスタンプ用鋼板としてめっき鋼板を用いる場合は、めっき性を確保するためにP含有量を0.05%以下とすることが好ましく、0.040%以下とすることがより好ましい。
Sは、鋼中に不純物として含有され、鋼を脆化させる元素である。そのため、S含有量は少ないほど好ましいが、S含有量が0.0200%を超えるとその悪影響が特に大きくなるので、S含有量は0.0200%以下とする。好ましいS含有量は0.0100%以下、0.0050%以下、または0.0030%以下である。
S含有量の下限は特に限定しないが、S含有量を過度に低下させることは製鋼コストの上昇を招くので、0.0001%以上含有させることが好ましい。
Alは、溶鋼を脱酸する作用を有する元素である。sol.Al含有量が0.001%未満であると脱酸が不十分となる。そのため、sol.Al含有量を0.001%以上とする。sol.Al含有量は好ましくは、0.010%以上、0.020%以上、または0.040%以上である。
一方、sol.Al含有量が高すぎる場合、変態点が上昇し、ホットスタンプの加熱過程で変態点以上の温度に鋼板を加熱することが困難となる。そのため、sol.Al含有量は2.500%以下とする。sol.Al含有量は好ましくは1.000%以下、0.500%以下、0.100%以下、または0.060%以下である。
Nは、鋼中に不純物として含有され、鋼の連続鋳造中に窒化物を形成する元素である。この窒化物はホットスタンプ後の靭性を劣化させるので、N含有量は低い方が好ましい。N含有量が0.0200%超であると、その悪影響が特に大きくなるので、N含有量は0.0200%以下とする。N含有量は好ましくは0.0100%未満、0.0080%未満、または0.0050%未満である。
N含有量の下限は特に限定しないが、N含有量を過度に低下させることは製鋼コストの上昇を招くので、Nを0.001%以上含有させることが好ましい。
Crは、フェライトを主体とする金属組織を有するホットスタンプ成形品(ホットスタンプ後の鋼板)の熱的安定性を向上させる作用を有する元素である。Cr含有量が0.30%未満である場合、上記作用による効果が十分に得られない。したがって、Cr含有量は0.30%以上とする。Cr含有量は、好ましくは0.50%以上、0.70%以上、または0.90%以上である。
一方、Cr含有量が2.00%以上であると、ホットスタンプ成形品の金属組織に含まれるマルテンサイトおよび/またはベイナイトの体積率が過剰となり、ホットスタンプ成形品の熱的安定性が劣化する。したがって、Cr含有量は2.00%未満とする。Cr含有量は好ましくは1.50%以下、1.20%以下、または1.00%以下である。
Nb:0~0.300%
V:0~0.300%
Zr:0~0.300%
Ti、Nb、VおよびZrは金属組織の微細化を通じ、ホットスタンプ成形品の引張強さを上昇させる作用を有する元素である。この効果を得るために、Ti、Nb、VおよびZrから選択される1種以上を必要に応じて含有させてもよい。
また、Ti、Nb、VおよびZrの含有量が多い場合、これらの元素の炭化物が多量に析出してホットスタンプ後の靭性が損なわれることが懸念される。したがって、Ti含有量は好ましくは0.060%未満、さらに好ましくは0.040%未満である。Nb含有量は好ましくは0.060%未満、さらに好ましくは0.040%未満である。V含有量は好ましくは0.200%未満、さらに好ましくは0.100%未満である。Zr含有量は好ましくは0.200%未満、さらに好ましくは0.100%未満である。
Cu:0~2.00%
Ni:0~2.00%
Mo、CuおよびNiは、ホットスタンプ成形品(ホットスタンプ後の鋼板)の引張強さを高める作用を有する。したがって、Mo、CuおよびNiから選択される1種以上を必要に応じて含有させてもよい。
そのため、含有させる場合でも、Mo、CuおよびNiの含有量は、それぞれ2.00%以下とする。好ましいMo含有量は0.50%以下であり、好ましいCu含有量は1.00%以下であり、好ましいNi含有量は1.00%以下である。
Bは、粒界に偏析してホットスタンプ後の鋼板の靭性を向上させる作用を有する元素である。この効果を得るため、必要に応じて含有させてもよい。
Mg:0~0.0100%
REM:0~0.1000%
Ca、MgおよびREMは、介在物の形状を調整することによりホットスタンプ後の靭性を向上させる作用を有する元素である。そのため、必要に応じて含有させてもよい。上記の効果を得たい場合には、Ca、MgおよびREMから選択される1種以上を、それぞれ0.0001%以上含有させることが好ましい。
一方、CaもしくはMgの含有量が0.0100%超である場合、またはREMの含有量が0.1000%超である場合、効果が飽和して過剰なコストが発生する。したがって、含有させる場合でも、CaおよびMgの含有量はそれぞれ0.0100%以下とし、REM含有量は0.1000%以下とする。
Biは、凝固組織を微細化することにより、ホットスタンプ後の靭性を向上させる作用を有する元素である。そのため、必要に応じて含有させてもよい。上記の効果を得たい場合には、Bi含有量は0.0001%以上であるのが好ましい。Bi含有量は、より好ましくは0.0003%以上であり、さら好ましくは0.0005%以上である。
一方、Bi含有量が0.0500%を超える場合、上記効果が飽和して過剰なコストが発生する。したがって、含有させる場合でも、Bi含有量は0.0500%以下とする。Bi含有量は、好ましくは0.0100%以下であり、より好ましくは0.0050%以下である。
本実施形態に係るホットスタンプ成形品の金属組織について説明する。本実施形態に係るホットスタンプ成形品の全部または一部は、以下に示す量のフェライト、マルテンサイトおよびベイナイトを含む金属組織を有する。金属組織に関する以下の説明において、「%」は、「体積率%」を意味する。
フェライトの体積率が60.0%以下であると、ホットスタンプ後の成形品の引張強さが700MPa以上となり、熱的安定性を確保することができない。そのため、フェライトの体積率を60.0%超とする。フェライトの体積率は、好ましくは70.0%超、さらに好ましくは80.0%超である。
フェライトの体積率の上限は特に定める必要がないが、ホットスタンプ成形品の強度を上昇させるために、98.0%未満とすることが好ましく、96.0%未満とすることがより好ましく、94.0%未満とすることがさらに好ましい。
上記フェライトには、ポリゴナルフェライトのほかに、ポリゴナルフェライトより転位密度の高い擬ポリゴナルフェライトおよびグラニュラーベイニティックフェライト、鋸歯状の粒界を有するアシキュラーフェライトが含まれる。熱的安定性の観点から、フェライト全体に対するポリゴナルフェライトの割合が、体積率で10.0%以上であることが好ましい。
ベイナイト:0%以上、20.0%未満
金属組織がマルテンサイトおよびベイナイトを含むと、ホットスタンプ成形品の熱的安定性が劣化する。そのため、マルテンサイトの体積率は10.0%未満、ベイナイトの体積率は20.0%未満とする。マルテンサイトの体積率は、5.0%未満とすることが好ましく、2.0%未満とすることがより好ましく、1.0%未満とすることがさらに好ましい。ベイナイトの体積率は、10.0%未満とすることが好ましく、5.0%未満とすることがより好ましく、2.0%未満とすることがさらに好ましい。
しかしながら、マルテンサイトおよびベイナイトは、ホットスタンプ成形品の強度を上昇させる作用を有するので、上記範囲内であれば金属組織に含まれていてもよい。マルテンサイトおよびベイナイトの体積率が0.1%未満であると、上記作用による効果が十分に得られない。そのため、強度を上昇させる場合には、マルテンサイトおよびベイナイトの体積率の下限値を、いずれも0.1%以上とすることが好ましく、0.5%以上とすることがより好ましい。
一方、パーライトを過剰に含有する場合、ホットスタンプ後の靭性が劣化する。そのため、パーライトの体積率を20.0%以下とすることが好ましく、10.0%以下とすることがより好ましい。
一方、残留オーステナイトを過剰に含有すると、ホットスタンプ後の靱性が低下する。そのため、残留オーステナイトの体積率を5.0%以下とすることが好ましく、3.0%以下とすることがより好ましい。
まず、ホットスタンプ成形品から試験片を採取し、鋼板の圧延方向に平行な縦断面を研磨した後、非めっき鋼板の場合は、鋼板表面から鋼板の板厚の1/4深さ位置、めっき鋼板の場合は、基材の鋼板とめっき層の境界から基材である鋼板の板厚の1/4深さ位置において組織観察する。ホットスタンプ成形品が、700MPa未満の引張強さを有する部分と、700MPa以上の引張強さを有する部分とを備えている場合、引張強さが700MPa未満となる部分から試験片を採取して観察を行う。
具体的には、研磨面をナイタール腐食した後、光学顕微鏡および走査電子顕微鏡(SEM)を用いて組織観察を行い、得られた組織写真に対して画像解析を行うことによって、フェライトとパーライトのそれぞれの面積率、およびベイナイト、マルテンサイト、残留オーステナイトの合計面積率を得る。その後、同様の観察位置に対し、レペラー腐食をした後、光学顕微鏡および走査電子顕微鏡(SEM)を用いて組織観察を行い、得られた組織写真に対して画像解析を行うことによって、残留オーステナイトとマルテンサイトの合計面積率を算出する。
また、同様の観察位置について、縦断面を電解研磨した後、電子線後方散乱パターン解析装置(EBSP)を備えたSEMを用いて、残留オーステナイトの面積率を測定する。
これらの結果に基づいて、フェライトとパーライト、ベイナイト、マルテンサイト、残留オーステナイトのそれぞれの面積率を得る。そして、面積率は体積率と等しいとして、測定された面積率を各組織の体積率とする。
本実施形態に係るホットスタンプ成形品の全部または一部は、母材鋼板の引張強さで700MPa未満である。これは、引張強さが700MPa以上であるとホットスタンプ成形品の熱的安定性を確保することができなくなるためである。好ましくは、ホットスタンプ成形品の全部または一部において、引張強さが600MPa未満、または560MPa未満である。一方、ホットスタンプ成形品の衝撃吸収性を向上させるためには、ホットスタンプ成形品の引張強さを440MPa以上とすることが好ましく、490MPa以上とすることがより好ましい。
本実施形態に係るホットスタンプ成形品は、170℃で20分間の熱処理を施した際の、ホットスタンプ前の引張強さに対する引張強さの低下量(ΔTS)が100MPa以下である。ΔTSは、60MPa以下であることが好ましく、30MPa以下であることがより好ましい。
フェライトを主体とする組織を有するホットスタンプ成形品において、塗装焼付時に強度が低下する理由は、フェライト中に存在する微細な鉄炭化物または微細な鉄炭素クラスターが、塗装焼付時の熱処理により粗大な鉄炭化物に変化するためであると考えられる。この微細な鉄炭化物または微細な鉄炭素クラスターの存在状態を直接的に定量的に評価することは容易ではないが、170℃で20分間の熱処理を施した後の、引張強さの低下量(ΔTS)によって間接的に評価できる。ΔTSが100MPa以下であれば、フェライト中における微細な鉄炭化物または微細な鉄炭素クラスターの生成が抑制され、熱的安定性に優れると判断される。
本実施形態に係るホットスタンプ成形品は、表面にめっき層を有していてもよい。表面にめっき層を備えることで、ホットスタンプ時におけるスケールの生成を防止し、さらにホットスタンプ成形品の耐食性を向上させることが可能になる。めっきの種類は、前記目的に適うものであればよく、特に限定されない。ホットスタンプ成形品のめっき層は、後述するように、めっき鋼板を用いてホットスタンプすることにより形成させることができる。めっき層の種類として、亜鉛系めっき鋼板やアルミニウム系めっき鋼板を用いてホットスタンプした、亜鉛系めっき層やアルミニウム系めっき層が例示される。
<ホットスタンプ用鋼板の化学組成>
ホットスタンプによって化学組成は実質的に変化しないので、ホットスタンプ用鋼板の化学組成は、上述したホットスタンプ成形品と同じ化学組成を有する。
本実施形態に係るホットスタンプ用鋼板の金属組織は、鉄炭化物を含み、鉄炭化物の化学組成(鉄炭化物中のMn含有量及びCr含有量)が下記(i)式を満足する。
[Mn]θ+[Cr]θ>2.5 ・・・(i)
但し、上記式中の各記号の意味は以下のとおりである。
[Mn]θ:鉄炭化物に含まれるFe、MnおよびCrの合計含有量を100原子%としたときの、鉄炭化物中のMn含有量(原子%)
[Cr]θ:鉄炭化物に含まれるFe、MnおよびCrの合計含有量を100原子%としたときの、鉄炭化物中のCr含有量(原子%)
まず、鋼板の任意の位置から試験片を採取し、鋼板の圧延方向に平行な縦断面を研磨した後、鋼板表面から板厚の1/4深さ位置においてレプリカ法により析出物を抽出する。この析出物を、透過型電子顕微鏡(TEM)を用いて観察し、電子線回折およびエネルギー分散型X線分析(EDS)により析出物の同定および組成分析を行う。
一方、鉄炭化物の体積率が過剰となると、ホットスタンプ後の鋼板の引張強さが高くなりすぎるとともに、熱的安定性が損なわれる。したがって、鉄炭化物の体積率は20%以下とすることが好ましく、15%以下とすることがより好ましい。
ホットスタンプ用鋼板の金属組織における体積率は、ホットスタンプ成形品の場合と同じ方法で求めることができる。
本実施形態に係るホットスタンプ成形品及び本実施形態に係るホットスタンプ用鋼板の好ましい製造方法について説明する。
本実施形態に係るホットスタンプ成形品の製造方法は、上述の化学組成および金属組織を有するホットスタンプ用鋼板を加熱する工程と、加熱されたホットスタンプ用鋼板に対してホットスタンプを行う工程と、を含む。ホットスタンプ工程では、金型による冷却及び成形が行われ、ホットスタンプ成形品が得られる。
加熱温度の上限は特に限定しないが、加熱温度が高すぎるとオーステナイトが粗大化し、ホットスタンプ成形品の強度が低下する。そのため、加熱温度は1000℃以下であることが好ましく、950℃以下であることがより好ましく、900℃以下であることがさらに好ましい。
また、ホットスタンプ成形品の耐食性を向上させるために、ホットスタンプ用鋼板、接合用鋼板には、表面にめっきが施されためっき鋼板を使用してもよい。めっき鋼板の種類は特に限定しないが、溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板、溶融アルミニウムめっき鋼板、溶融Zn-Al合金めっき鋼板、溶融Zn-Al-Mg合金めっき鋼板、溶融Zn-Al-Mg-Si合金めっき鋼板、電気亜鉛めっき鋼板および、電気Ni-Zn合金めっき鋼板等が例示される。
本実施形態に係るホットスタンプ用鋼板の製造方法は、上述の化学組成を有するスラブに対して、熱間圧延を施した後、800℃以下の温度域で巻取って熱延鋼板とする熱間圧延工程と、上記熱延鋼板を650℃を超える温度域まで加熱する熱延板焼鈍を施して熱延焼鈍鋼板とする熱延板焼鈍工程とを含む。
真空溶解炉を用いて溶鋼を鋳造し、表1に示す化学組成を有する鋼A~Rを製造した。表1中のAc1点およびAc3点は、鋼A~Rの冷延鋼板を2℃/秒で加熱した際の熱膨張変化から求めた。また、表1中のAr3点は、鋼A~Mの冷延鋼板を950℃に加熱した後10℃/秒で冷却した際の熱膨張変化から求めた。鋼A~Rを1200℃に加熱し60分間保持した後、表2に示す熱延条件で熱間圧延を行った。
鋼Rを用いた試験番号34および35は、鋼のCr含有量が低すぎるため、ΔTSが大きかった。
化学組成は本発明の範囲内であるが、ホットスタンプ用鋼板の金属組織が本発明の範囲から外れる鋼板を用いた比較例の試験番号26、28、および、30は、ホットスタンプ成形品のΔTSが100MPa以上であり、熱的安定性が劣っていた。
具体的には、鋼Nを用いた試験番号26、および、鋼Pを用いた試験番号30は、熱延板焼鈍を行っていないために、ホットスタンプ用鋼板の金属組織において鉄炭化物中のMn含有量とCr含有量の和が低く、ΔTSが大きかった。
鋼Oを用いた試験番号28は、熱延板焼鈍工程における加熱温度が低すぎるために、ホットスタンプ用鋼板の金属組織において鉄炭化物中のMn含有量とCr含有量の和が低く、ΔTSが大きかった。
真空溶解炉を用いて溶鋼を鋳造し、実施例1において、表1に示した化学組成を有する鋼A~Cを製造した。鋼A~Cを用い、実施例1と同様に、表5に示す条件で、熱間圧延、熱延板焼鈍、冷間圧延、および、焼鈍を行い、次いでめっき処理を行い、溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼板、および、溶融アルミニウムめっき鋼板(ホットスタンプ用鋼板)を製造した。
Claims (21)
- ホットスタンプ成形品であって、
前記ホットスタンプ成形品の全部または一部が、
質量%で、
C:0.001%以上0.080%未満、
Si:2.50%以下、
Mn:0.01%以上0.50%未満、
P:0.200%以下、
S:0.0200%以下、
sol.Al:0.001~2.500%、
N:0.0200%以下、
Cr:0.30%以上2.00%未満、
Ti:0~0.300%、
Nb:0~0.300%、
V:0~0.300%、
Zr:0~0.300%、
Mo:0~2.00%、
Cu:0~2.00%、
Ni:0~2.00%、
B:0~0.0200%、
Ca:0~0.0100%、
Mg:0~0.0100%、
REM:0~0.1000%、
Bi:0~0.0500%、
残部:Feおよび不純物である化学組成を有し、
金属組織が、体積%で、
フェライト:60.0%超、
マルテンサイト:0%以上10.0%未満、
ベイナイト:0%以上20.0%未満、を含み、
引張強さが、700MPa未満であり、
170℃で20分間の熱処理を施した後の、前記引張強さの低下量であるΔTSが100MPa以下である、
ホットスタンプ成形品。 - 前記化学組成が、質量%で、
Ti:0.001~0.300%、
Nb:0.001~0.300%、
V:0.001~0.300%、および、
Zr:0.001~0.300%、
から選択される1種以上を含有する、
請求項1に記載のホットスタンプ成形品。 - 前記化学組成が、質量%で、
Mo:0.001~2.00%、
Cu:0.001~2.00%、および、
Ni:0.001~2.00%、
から選択される1種以上を含有する、
請求項1または請求項2に記載のホットスタンプ成形品。 - 前記化学組成が、質量%で、
B:0.0001~0.0200%、
を含有する、
請求項1から請求項3までのいずれか一項に記載のホットスタンプ成形品。 - 前記化学組成が、質量%で、
Ca:0.0001~0.0100%、
Mg:0.0001~0.0100%、および、
REM:0.0001~0.1000%、
から選択される1種以上を含有する、
請求項1から請求項4までのいずれか一項に記載のホットスタンプ成形品。 - 前記化学組成が、質量%で、
Bi:0.0001~0.0500%、
を含有する、
請求項1から請求項5までのいずれか一項に記載のホットスタンプ成形品。 - 表面にめっき層を有する、
請求項1から請求項6までのいずれか一項に記載のホットスタンプ成形品。 - 化学組成が、質量%で、
C:0.001%以上0.080%未満、
Si:2.50%以下、
Mn:0.01%以上0.50%未満、
P:0.200%以下、
S:0.0200%以下、
sol.Al:0.001~2.500%、
N:0.0200%以下、
Cr:0.30%以上2.00%未満、
Ti:0~0.300%、
Nb:0~0.300%、
V:0~0.300%、
Zr:0~0.300%、
Mo:0~2.00%、
Cu:0~2.00%、
Ni:0~2.00%、
B:0~0.0200%、
Ca:0~0.0100%、
Mg:0~0.0100%、
REM:0~0.1000%、
Bi:0~0.0500%、
残部:Feおよび不純物であり、
金属組織が、鉄炭化物を含み、前記鉄炭化物中のMn含有量及びCr含有量が下記(i)式を満足する、
ホットスタンプ用鋼板。
[Mn]θ+[Cr]θ>2.5 ・・・(i)
但し、上記式中の各記号の意味は以下のとおりである。
[Mn]θ:鉄炭化物に含まれるFe、MnおよびCrの合計含有量を100原子%としたときの、原子%での鉄炭化物中のMn含有量
[Cr]θ:前記鉄炭化物に含まれるFe、MnおよびCrの合計含有量を100原子%としたときの、原子%での鉄炭化物中のCr含有量 - 前記化学組成が、質量%で、
Ti:0.001~0.300%、
Nb:0.001~0.300%、
V:0.001~0.300%、および、
Zr:0.001~0.300%、
から選択される1種以上を含有する、
請求項8に記載のホットスタンプ用鋼板。 - 前記化学組成が、質量%で、
Mo:0.001~2.00%、
Cu:0.001~2.00%、および、
Ni:0.001~2.00%、
から選択される1種以上を含有する、
請求項8または請求項9に記載のホットスタンプ用鋼板。 - 前記化学組成が、質量%で、
B:0.0001~0.0200%、
を含有する、
請求項8から請求項10までのいずれか一項に記載のホットスタンプ用鋼板。 - 前記化学組成が、質量%で、
Ca:0.0001~0.0100%、
Mg:0.0001~0.0100%、および、
REM:0.0001~0.1000%、
から選択される1種以上を含有する、
請求項8から請求項11までのいずれか一項に記載のホットスタンプ用鋼板。 - 前記化学組成が、質量%で、
Bi:0.0001~0.0500%、
を含有する、
請求項8から請求項12までのいずれか一項に記載のホットスタンプ用鋼板。 - 表面にめっき層を有する、
請求項8から請求項13までのいずれか一項に記載のホットスタンプ用鋼板。 - 請求項1から請求項6までのいずれか一項に記載のホットスタンプ成形品を製造する方法であって、
請求項8から請求項13までのいずれか一項に記載のホットスタンプ用鋼板を加熱温度T℃まで加熱する加熱工程と、
前記加熱工程後の前記ホットスタンプ用鋼板に対してホットスタンプを行うホットスタンプ工程と、を備える、
ホットスタンプ成形品の製造方法。 - 請求項1から請求項6までのいずれか一項に記載のホットスタンプ成形品を製造する方法であって、
請求項8から請求項13までのいずれか一項に記載のホットスタンプ用鋼板を、接合用鋼板と接合して接合鋼板とする接合工程と、
前記接合工程後の接合鋼板を加熱温度T℃まで加熱する加熱工程と、
前記加熱工程後の前記接合鋼板に対してホットスタンプを行うホットスタンプ工程と、を備える、
ホットスタンプ成形品の製造方法。 - 請求項7に記載のホットスタンプ成形品を製造する方法であって、
請求項14に記載のホットスタンプ用鋼板を加熱温度T℃まで加熱する加熱工程と、
前記加熱工程後の前記鋼板に対してホットスタンプを行うホットスタンプ工程と、を備える、
ホットスタンプ成形品の製造方法。 - 請求項7に記載のホットスタンプ成形品を製造する方法であって、
請求項14に記載のホットスタンプ用鋼板を、接合用鋼板と接合して接合鋼板とする接合工程と、
前記接合工程後の接合鋼板を加熱温度T℃まで加熱する加熱工程と、
前記加熱工程後の前記接合鋼板に対してホットスタンプを行うホットスタンプ工程と、を備える、
ホットスタンプ成形品の製造方法。 - 前記加熱工程において、前記加熱温度T℃が、前記ホットスタンプ用鋼板のAc1点を超える温度であり、
前記ホットスタンプ工程において、ホットスタンプ開始温度が(T-300)℃以上の温度である、
請求項15~18のいずれか一項に記載のホットスタンプ成形品の製造方法。 - 請求項8から請求項14までのいずれか一項に記載のホットスタンプ用鋼板を製造する方法であって、
化学組成が、質量%で、C:0.001%以上0.080%未満、Si:2.50%以下、Mn:0.01%以上0.50%未満、P:0.200%以下、S:0.0200%以下、sol.Al:0.001~2.500%、N:0.0200%以下、Cr:0.30%以上2.00%未満、Ti:0~0.300%、Nb:0~0.300%、V:0~0.300%、Zr:0~0.300%、Mo:0~2.00%、Cu:0~2.00%、Ni:0~2.00%、B:0~0.0200%、Ca:0~0.0100%、Mg:0~0.0100%、REM:0~0.1000%、Bi:0~0.0500%、残部:Feおよび不純物であるスラブに対して、熱間圧延を施した後、800℃以下の温度域で巻取って熱延鋼板とする熱間圧延工程と、
前記熱延鋼板に650℃を超える温度域まで加熱する熱延板焼鈍を施して熱延焼鈍鋼板とする熱延板焼鈍工程と、を備える、
ホットスタンプ用鋼板の製造方法。 - さらに、前記熱延板焼鈍工程後の前記熱延焼鈍鋼板に、
任意に、冷間圧延、及び焼鈍のいずれかまたは両方を行った後、めっきを行うめっき工程を備える、
請求項20に記載のホットスタンプ用鋼板の製造方法。
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JP2021031745A (ja) * | 2019-08-27 | 2021-03-01 | 株式会社神戸製鋼所 | 低強度ホットスタンプ用鋼板、ホットスタンプ部品およびホットスタンプ部品の製造方法 |
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- 2018-10-02 CA CA3077793A patent/CA3077793A1/en not_active Abandoned
- 2018-10-02 BR BR112020005755-0A patent/BR112020005755A2/pt not_active IP Right Cessation
- 2018-10-02 CN CN201880063548.7A patent/CN111164229B/zh active Active
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JPWO2020204037A1 (ja) * | 2019-04-01 | 2021-12-02 | 日本製鉄株式会社 | ホットスタンプ成形品およびホットスタンプ用鋼板、並びにそれらの製造方法 |
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JP7151878B2 (ja) | 2019-04-01 | 2022-10-12 | 日本製鉄株式会社 | ホットスタンプ成形品およびホットスタンプ用鋼板、並びにそれらの製造方法 |
JP2021031745A (ja) * | 2019-08-27 | 2021-03-01 | 株式会社神戸製鋼所 | 低強度ホットスタンプ用鋼板、ホットスタンプ部品およびホットスタンプ部品の製造方法 |
WO2021039499A1 (ja) * | 2019-08-27 | 2021-03-04 | 株式会社神戸製鋼所 | 低強度ホットスタンプ用鋼板、ホットスタンプ部品およびホットスタンプ部品の製造方法 |
JP7235621B2 (ja) | 2019-08-27 | 2023-03-08 | 株式会社神戸製鋼所 | 低強度ホットスタンプ用鋼板、ホットスタンプ部品およびホットスタンプ部品の製造方法 |
Also Published As
Publication number | Publication date |
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BR112020005755A2 (pt) | 2020-10-13 |
TWI683002B (zh) | 2020-01-21 |
US11565299B2 (en) | 2023-01-31 |
EP3693485A1 (en) | 2020-08-12 |
CN111164229A (zh) | 2020-05-15 |
MX2020003896A (es) | 2020-08-20 |
KR102404647B1 (ko) | 2022-06-02 |
KR20200047634A (ko) | 2020-05-07 |
JP6525123B1 (ja) | 2019-06-05 |
EP3693485A4 (en) | 2021-01-20 |
CA3077793A1 (en) | 2019-04-11 |
JPWO2019069938A1 (ja) | 2019-11-14 |
CN111164229B (zh) | 2022-01-14 |
US20200306812A1 (en) | 2020-10-01 |
TW201923096A (zh) | 2019-06-16 |
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